That is ... very odd and I've never heard of that before. If you have one nearby, I'd take her to a vet that does necropsies. If you don't want to spend the money, then bury her before she starts to smell and I'm very sorry for your loss I don't know what to tell you happened there.

Sounds like possibly kidney failure! When the kidney's shut down the large amount of water then goes into the lungs. Could also have been bad water...was the water fresh...please understand I am not pointing a finger...just trying to figure this out for you.

i always change my pets water daily, so it shouldnt have been the water, and my corn snake gets the same kind of water and gets her water changed just the same as the boa did. her last meal was only hours before she died, which is why i thought maybe she choked. but it was just a fuzzy, shed eaten a million of them before.

Sorry to hear of your loss. Is there any way your snake could have come into contact with an exposed wire or part of any electrical accessory in your enclosure? These do not only burn but can electrocute and cause the heart or other organs to fail. The fact that she had drank water is highly unlikely the cause as she drinks small quantities and only as much as she needs. If she was really sick the probability that she would drink is also reduced. Being wet on the other hand could have increased the risk and seiousness of an electrical contact.